Multiple-band gamma matched antenna



16, 1960 c. w. LAMB 2,949,607

MULTIPLE-BAND GAMMA MATCHED ANTENNA Filed Sept. 5. 1958 Carl W. LambINVENTOR.

4052". BY m, 25

MULTIPLE-BAND GAMMA MATCHED ANTENNA Carl W. Lamb, 4301 Caster Road,Knoxville 18, Tenn.

Filed Sept. 5, 1958, Ser. No. 759,327

4 Claims. (Cl. 343-722) This invention relates generally to antennas andmore particularly to an improved match to be utilized particularly inmulti-band antennas.

It is old and well known in the antenna art that a single antenna may beutilized for the transmission or reception of a multiple number offrequency bands by utilizing electrical traps along the length of the antenna rod. That is, by electrically serially connecting resonantcircuits along the length of the antenna rod, effective antenna rodlengths of half-wave lengths may be established for desired frequencies.It is of course apparent that proper half-wave lengths utilized withcorresponding wave frequencies result in minimum standing wave ratiosand more efiicient transmission and reception of radio waves. In recentyears, the radio amateur or the ham has come to utilize a tri-bandantenna having the traps noted above for the reception and transmissionof the ten, fifteen and twenty meter bands. The traps utilized aremerely resonant circuits which pass certain frequencies but refuse topass other frequencies. Of course, the higher the frequency band, theshorter is the wave length and the shorter is the antenna lengthutilized in conjunction with this particular wave length. Therefore, inthe construction of a multi-band antenna, traps closest to the antennacenter or feed line are designed to pass the lower frequencies or longerwave lengths but to present an open circuit to the higher frequenciesand, therefore, a shorter antenna rod length.

In the utilization of the above noted multi-band antennas, recentdevelopments in the antenna field have included gamma matches formatching the antenna impedance to the antenna feed line impedance forthe maximum efficient transfer of the energy between the antenna and thefeed line. Of the gamma matches developed to date for utilization inconjunction with the multi-band antenna, capacitive elements areelectrically connected to the antenna rod at proper points therealongand are further electrically connected to a gamma rod which electricallyproceeds to one side of the antenna feed line. In the utilization of atri-band antenna, three separate gamma matches must of course beutilized for the effective energy transfer of the three different bandsfor which the antenna was designed. The necessity of utilizing threeseparate gamma rods limits somewhat the electrical and mechanicalefficiency of the antenna. More particularly, the utilization of threedistinct gamma rods increases the expense, weight, and wind resistanceof the antenna. not designed to be reflecting parasitic elements, theydistort the radiating pattern adjacent the antenna. In view of thesedeficiencies in the presently used conventional tri-band antennas, thefollowing recites the particulars of an improved multi-band antennamatch which obviates these deficiencies.

Accordingly, it is the principal object of this invention to provide anovel multi-band antenna match which while being electrically moreefficient than hereto known Further, since generally the gamma rods are2,949,607. Patented Aug. 16, 1960 devices is less expensive, lighter,and presents less wind resistance.

It is a further object of this invention to provide a novel multi-bandantenna match which decreases the distortion often generated in theradiating pattern adjacent the antenna.

It is a still further object of this invention to provide a moreeificient gamma match for multi-band antennas which utilizes a seriesresonant circuit for more eflicient discrimination between the bands.

In accordance with the above stated objects, below is particularlydescribed the construction and utilization of the novel gamma match fora multi-band antenna. Whereas formerly a separate gamma rod was utilizedwith each capacitive element corresponding to a match for each of thebands, the applicant utilizes his capacitive elements on a single gammarod supported below the antenna rod. Each capacitive element is formedby placing a conductive sleeve about the gamma rod at the desiredmatching point with a tubular insulator therebetween. The conductivesleeve is electrically connected to the antenna rod, while the gamma rodis terminally connected to one side of the antenna feed line. Thecapacitive elements are of such values that, of course, only one iselectrically effective for each hand. If desired, the electricalconnection between the sleeve and the antenna rod may include a seriallyconnected inductive element providing a series trap for aiding theconventional trap utilized on the antenna rod. This latter utilizationprovides better discrimination between the different bands.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

Figure 1 is an elevational view of the antenna construction showing thesingle gamma rod;

Figure 2 is an enlarged fragmentary sectional view of the gamma matchportion of the antenna;

Figure 3 is a sectional view taken substantially along the plane 33 ofFigure 2;

Figure 4 is a sectional view taken substantially along plane 4-4 ofFigure 1;

Figure 5 is a schematic circuit diagram of the antenna and matchillustrating the resonant t-rap circuits and capacitive matchingelements; and

Figure 6 is a fragmentary elevational view of a modia half-wave lengthfor desired frequency bands. Noting- Figure 5, point 18 is the center ofthe antenna rod and the point of connection of one side of the feedline. Trap 12 presents an open circuit to the highest frequency forwhich the antenna is desired to be utilized. Therefore, the antenna rodlength between point 18 and trap 12 should be equal to one quarter of awave length of the wave which has a frequency limited by the trap 12.Likewise, the antenna rod distance between point 18 and trap 14 shouldbe equal to one quarter of a wave length of a wave having the frequencyto which trap 14 presents an open circuit.

Capacitive elements 20, 22 and 24 are electrically connected between theantenna rod 10 and gamma rod 26 for forming a gamma match for matchingthe impedance of the antenna rod 10 to the feed line 28. Moreparticularly referring to Figure 2, the capacitive elements include aconductive sleeve 30 concentrically placed about the gamma rod 26 with atubular insulator 32 sandwiched therebetween. It of course should beapparent that electrical capacitance exists between sleeve 30 and gammarod 26. Capacitive element is electrically connected fromthe sleeve to acollar 34 and thence to an aluminum Wire 36 to a collar 38 electricallyin contact with the antenna rod 10. Capacitive element 22 is electrically connected to the antenna rod through aluminum wire 38, whilecapacitive element 24 is electrically connected through aluminum wire40.

It should be apparent that when the antenna is excited with its highestfrequency radio power, the traps 12 (only one shown) electrically showan open circuit and only the antenna portion on both sides of centerpoint 18 to trap 12 utilizes power. Also at this frequency only thecapacitive element 20 and the portion of the gamma rod between theelement 20 and the feed line matches the antenna. The other traps,antenna lengths, capacitive elements and gamma rod lengths will have noelectrical elfect at all. Likewise, when the midfiequency is utilized,traps 14 show an open circuit and the antenna becomes equal to twice thelength between point 18 and trap 14 and then capacitive element 22 andthe gamma rod length between capacitive element 22 and the feed line isutilized. Again the other traps, antenna lengths, capacitive elementsand gamma rod lengths are not used. The apparent exclusive of theundesired capacitive elements and antenna lengths should be apparentupon the realization of the parallel electrical relationship between thecapacitive elements.

More particularly referring to the mechanical or structural features ofthe invention, Figure 3 clearly shows the particulars of the connectionbetween the antenna rod '10 and the gamma rod 26. The electrical circuitextends from the antenna rod 10 to the collar 37 held tightly by boltand nut 42 and 44 to the aluminum wire 38, thence to the collar 34, tothe sleeve 30, across the tubular insulator 32 to the gamma rod 26. Abolt 46 and nut 48 are utilized in conjunction with the collar 54.

Figure 4 shows the structural features of the coaxial panel connector.Intially, a collar 50 is utilized about the antenna rod 10 and is heldby bolt 52 and nut 54 and electrically communicates with the bolt 56 andnut 58 which are electrically connected to the threaded sleeve 60through member 62. The gamma rod 26 electrically extends through the pin64 to a central contact within the sleeve 60 (not shown). Of course,insulation within the sleeve 60 insulates the central contact from thesleeve 60 whereby the coaxial connector may be threaded over thethreaded sleeve 60 and extended to two sides of a feed line forconnection to the gamma rod 26 and antenna lit.

A further modification of the invention is illustrated in Figure 6wherein inductive elements '70, 72 and 74 are shown utilized with thecapacitive elements 20, 22 and 24-. The match established between theantenna and feed line should not be disturbed, but the seriescombination of the inductive and capacitive elements establishes aseries trap at desired frequencies to aid the parallel trapcoils 12, 14and 16. The electrical features of Figure 6 have proven extremelysatisfactory and discriminating. Aside from the addition of theinductive elements 70, 72 and 74, the features remain identical to thosedescribed above.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention asclaimed.

What is claimed as new is as follows:

1. An improved match for a multi-band antenna system having an antennafeed line, an antenna rod and a plurality of electrically resonant trapsconnected thereto comprising a single gamma rod terminally electricallyconnected to said antenna feed line and a plurality of capacitiveelements electrically connecting said gamma rod to said antenna rod atvarying points along said rods, said capacitive elements including aconductive sleeve concentrically carried around said gamma rod and atubular insulator sandwiched between said sleeve and said gamma rod,said sleeve being electrically connected to said antenna rod.

2. The combination of claim 1 wherein said electrical connection betweensaid sleeve and said antenna rod includes a serially connected inductiveelement.

3. A multi-band antenna comprising an antenna rod, resonant trapselectrically connected to said antenna rod for establishing properantenna half-wave lengths for desired frequency bands, an antenna feedline, a gamma match electrically connected between said antenna rod andsaid feed line for matching the respective impedances thereof, saidgamma match including a single gamma rod terminally connected to saidfeed line, and a plurality of capacitive elements electrically connectedbetween said gamma rod and said antenna rod, said capacitive elementsincluding a conductive sleeve concentrically carried around said gammarod and a tubular insulator sandwiched between said sleeve and saidgamma rod, said sleeve being electrically connected to said antenna rod.

4. A multi-band antenna comprising an antenna rod, resonant trapselectrically connected to said antenna rod for establishing properantenna half-wave lengths for desired frequency bands, an antenna feedline, a gamma match electrically connected between said antenna rod andsaid feed line for matching the respective impedances thereof, saidgamma match including a single gamma rod terminally connected to saidfeed line, and a plurality of capacitive elements electrically connectedbetween said gamma rod and said antenna rod, said capacitive elementsincluding a conductive sleeve concentrically carried around said gammarod and a tubular insulator sandwiched between said sleeve and saidgamma rod, a plurality of inductive elements, each of said inductiveelements electrically connected between a sleeve and said antenna rod.

References Cited in the file of this patent UNITED STATES PATENTS2,578,973 Hills Dec. 18, 1951 2,648,771 Cork Aug. 11, 1953 2,719,920Ellis Oct. 4, 1955 2,861,267 Arrasmith Nov. 18, 1958 OTHER REFERENCESPub. I: Simple Gamma-Match Construction, Reynolds, QST, vol. 41, July1957, page 30.

Pub. II: A Matching System for a Three-Band Beam, McCoy, QST, vol. 41,November 1957, pages 40 and 41.

